Stockholders' Equity (Details) (USD $)	0 Months Ended	3 Months Ended		1 Months Ended
	Feb. 13, 2014	Mar. 31, 2014	Mar. 31, 2013	Apr. 30, 2014 Subsequent Event
Components of basic and diluted earnings per share
Net income from continuing operations		$ 74,864,000	$ 53,863,000
Weighted average shares outstanding - basic		85,019,000	85,592,000
Dilutive potential shares from stock options			1,000
Weighted average shares outstanding - diluted		85,019,000	85,593,000
Earnings per share:
Earnings per share from continuing operations, basic and diluted (in dollars per share)		$ 0.88	$ 0.63
Dividends
Dividends accrued, per share (in dollars per share)	$ 0.34	$ 0.34
Dividends to be paid		$ 28,900,000
Common stock repurchases
Shares repurchased in the open market or privately		280,186	81,701
Common stock repurchases
Shares repurchased from employees to cover minimum income tax withholdings		2,667	2,601	386,165